The present invention generally relates to high resolution multipoint probes for establishing an electrical connection to a test sample. More specifically, the present invention relates to the prevention of short circuiting in such multipoint probes manufactured of silicon based wafers.
High resolution multipoint probes, and the manufacturing, use, and handling of such probes, are disclosed in EP1095282 (A2), EP1698905 (A2), EP1466182 (A1), EP1610131 (A1), EP1640730 (A1), EP1686387 (A1), EP1782078 (A1), EP1775594 (A1), EP1780550 (A1), EP2016433 (A1), EP1949115 (A1), EP1946124 (A1), EP2293086 (A1), EP1970714 (A1), EP2101181 (A1), EP2132578 (A1), EP2141503 (A1), EP2198316 (A1), EP2237052 (A1), EP2307892 (A1), EP2414846 (A1). Reference is made to the above-mentioned documents. The US patents and published US patent applications claiming the same priorities as specified for the above-mentioned patent documents are hereby incorporated by reference in the present specifications.
High resolution in multipoint probes may be achieved by manufacturing them from a silicon based wafer. The high resolution requires that the contact electrodes of the multipoint probe are positioned close to one another. This means that the traces leading to the contact electrodes are also positioned close to one another, at least at the probe tip. This means that the width of the traces at the probe tip is limited by the resolution of the contact electrodes. The open structure of multipoint probes manufactured from silicon based wafers is sensitive to short circuiting between the traces and other structures of the multipoint probe, in particular for probes with a contact electrode separation below 1 μm. The short circuiting may be caused in the manufacturing process, in which the risk of short circuiting typically increases with increased lengths of the traces. Short circuiting may also be caused when the high resolution multipoint probe is employed in a measurement.
It is an object of the present invention to provide an accurate high resolution multipoint probe with a low risk of internal short circuiting. It is a further object of the present invention to reduce the risk of short circuiting when employing the multipoint probe in a measurement.
The above objects are according to a first aspect of the present invention obtained by a multipoint probe for establishing an electrical connection between a test apparatus and a test sample, the multipoint probe comprising: a base constituting a plate-like structure defining a first top surface, a first bottom surface, and a circumferential first rim interconnecting the first top surface and the first bottom surface, a probe tip provided at the first top surface of the base and freely extending from the circumferential first rim, the probe tip comprising a first plurality of contact electrodes for contacting and establishing an electrical connection to the test sample, a second plurality of contact pad supports provided on the first top surface and supported by the base, and each contact pad support having an outline defining a contact pad support boundary enclosing a contact pad support area, a third plurality of trace supports provided on the first top surface and supported by the base, each trace support having an outline defining a trace support boundary enclosing a trace support area, and each trace support comprising a wide portion connected to a contact pad support of the second plurality of contact pad supports and individually defining a first length and a first width and a narrow portion connected to the probe tip and individually defining a second length and a second width, the first length being longer than the second length and the first width being greater than the second width, a fourth plurality of contact pads for connecting to the test apparatus, each contact pad being individually supported by a contact pad support of the second plurality of contact pad supports and being constituted by a metallic layer covering the contact pad support area of the supporting contact pad support, and a fifth plurality of traces, each trace being individually supported by a trace support of the third plurality of trace supports and being constituted by a metallic layer covering the trace support area of the supporting trace support, each trace individually interconnecting a contact pad of the fourth plurality of contact pads and a contact electrode of the first plurality of contact electrodes, the first plurality, the second plurality, the third plurality, the fourth plurality, and the fifth plurality being equal in numbers, the first top surface comprising first intermediate surfaces, each first intermediate surface individually interconnecting a pair of neighbouring trace supports of the third plurality of trace supports at their respective wide portions, the first top surface comprising second intermediate surfaces, each second intermediate surface individually interconnecting a pair of neighbouring trace supports of the third plurality of trace supports at their respective narrow portions, and the first intermediate surfaces being provided on a first level, the second intermediate surfaces being provided on a second level above the first level relative to the base, and the contact pad support area and the trace support areas being provided on a third level above the first level and the second level relative to the base.
The first width of the wide portion of each trace support of the third plurality of trace supports may be the average width of the wide portion. Alternatively, the first width of the wide portion of each trace support of the third plurality of trace supports may be the minimum width of the wide portion. The second width of the narrow portion of each trace support of the third plurality of trace supports may be the average width of the narrow portion. Alternatively, the second width of the narrow portion of each trace support of the third plurality of trace supports may be the maximum width of the narrow portion.
The providing of the first intermediate surfaces on a first level, the second intermediate surfaces on a second level above the first level relative to the base, and the contact pad support area and the trace support areas on a third level above the first level and the second level relative to the base has the effect of reducing the risk of short circuiting with a maintained spatial resolution of the traces at the probe tip. This effect is further enhanced by the specification that the first length is longer than the second length. That the first width is greater than the second width allows for the first level and the second level to be spaced further apart, which means that the risk for short circuiting can be further reduced.
The first level and the second level may be spaced apart by a first distance, and the second level and the third level may be spaced apart by a second distance, and the first distance may be greater than the second distance. This further reduces the risk for short circuiting.
The first level and the second level may be spaced apart by a first distance, and the second level and the third level may be spaced apart by a second distance, and the first distance may be greater than 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, or 2 μm, and/or the second distance may be smaller than 2 μm, 1.5 μm, 1 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, or 0.3 μm.
The first level may define a first plane, the second level may define a second plane parallel to the first plane, and the third level may define a third plane parallel to the second plane.
Each trace support of the third plurality of trace supports may comprise a tapering portion individually interconnecting the wide portion and the narrow portion of the trace support, and the tapering portion may define a narrowing width when going from the wide portion to the narrow portion. Each second intermediate surface may interconnect a pair of neighbouring trace supports of the plurality of trace supports at their respective tapering portions. This has the effect that the transition from the wide portion to the narrow portion will not break if it is subjected only to the undercutting process of the narrow portion.
The first top surface may comprise third intermediate surfaces, each third intermediate surface individually interconnecting a pair of neighbouring contact pad supports of the second plurality of contact pad supports, and the third intermediate surfaces are provided on the first level. This has the effect that that the risk of short circuiting the contact pads is reduced.
Each trace support of the third plurality of trace supports may define a first trace support undercut provided at the wide portion and at the trace support boundary and partly undercutting the trace supports area at the wide portion of the trace support. This has the effect that the risk of short circuiting is further reduced.
The first trace support undercut may define a first undercutting depth being greater than 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, or 900 nm.
Each trace support of the third plurality of trace supports may define a second trace support undercut provided at the narrow portion and at the trace support boundary and partly undercutting the trace supports area at the narrow portion of the trace support. This has the effect that the risk of short circuiting is further reduced.
The second trace support undercut may define a second undercutting depth being smaller than 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, or 50 nm.
The first trace support undercut may be deeper than the second trace support undercut. This has the effect that the risk of short circuiting is further reduced.
Each contact pad support of the second plurality of contact pad supports may define a contact pad support undercut provided at the contact pad support boundary and partly undercutting the contact pad support area of the contact pad support.
The first trace support undercut and the contact pad support undercut may have approximately the same undercutting depth. This has the effect that the multipoint probe is easier to manufacture.
The trace support area may be convex at the narrow portions of each trace support of the third plurality of trace supports. This has the effect that the supported traces do not present any sharp corners, and it is contemplated that the risk is reduced that small short circuiting particles will get stuck between closely positioned traces when converging on a probe tip.
The probe tip may further comprise: a tip base having a proximal end and a distal end and constituting a plate-like tip structure defining a second top surface, a second bottom surface, and a second rim interconnecting the second top surface and the second bottom surface, the second top surface connecting to the second rim along a first side edge extending from the proximal end to the distal end, a second side edge on the opposite side of the tip structure relative to the first side edge and extending from the proximal end to the distal end, and a front edge interconnecting the first side edge and the second side edge, the tip base being connected at its proximal end to the base, a sixth plurality of contact electrode supports provided on the second top surface and supported by the tip base, each contact electrode support being elongated and extending from the proximal end in a direction towards the distal end, and each contact electrode support having an outline defining a contact electrode support boundary enclosing a contact electrode support area, and each contact electrode of the first plurality of contact electrodes being individually supported by a contact electrode support of the sixth plurality of contact electrode supports and being constituted by a metallic electrode layer covering the contact electrode support area of the supporting contact electrode support, the first plurality and the sixth plurality being equal in numbers, the second top surface comprising fourth intermediate surfaces, each fourth intermediate surface individually interconnecting a pair of neighbouring contact electrode supports of the sixth plurality of contact electrode supports, and the fourth intermediate surfaces being provided on a fourth level, the contact electrode support areas being provided on a fifth level above the fourth level relative to the tip base, the fourth level being the same as the second level and the fifth level being the same as the third level.
The fourth intermediate surfaces being provided on a fourth level and the contact electrode support areas being provided on a fifth level has the effect that the risk for short circuiting in the probe tip as such is reduced. Further, particles may get stuck on the probe tip when it is repeatedly used. The contact electrodes protrude from the tip base, which reduces the risk that particles on the test sample will get stuck on the fourth intermediate surfaces of the second top surface, which means that the risk of particles short circuiting the probe arms in repeated measurements is reduced.
The front edge is straight. This has the advantage that the risk of contacting the test sample with the tip base is reduced, which could damage the test sample and cause particles to be released from the test sample that would land on the multi-point probe and cause it to short circuit.
The sixth plurality of electrode supports may extend to and terminates at the front edge. This further reduces the risk of damaging the test sample and generating short circuiting particles when contacting a test sample.
The sixth plurality of electrode supports extends to and terminates at a third distance from the front edge. This has the effect that the distal ends of the contact electrodes can be defined independent of the front edge, which means that their positions can be more accurately determined, thus increasing the accuracy of the contacting.
The third distance may be in one or more of the ranges 0.1 μm to 2 μm, 0.2 μm to 1.5 μm, 0.3 μm to 1 μm, 0.4 μm to 0.9 μm, 0.5 μm to 0.8 μm, 0.6 μm to 0.7 μm, 0.1 μm to 0.2 μm, 0.2 μm to 0.3 μm, 0.3 μm to 0.4 μm, 0.4 μm to 0.5 μm, 0.5 μm to 0.6 μm, 0.6 μm to 0.7 μm, 0.7 μm to 0.8 μm, 0.8 μm to 0.9 μm, 0.9 μm to 1 μm, 1 μm to 1.5 μm, and 1.5 μm to 2 μm.
Each contact electrode support of the sixth plurality of contact electrode supports may define a contact electrode support undercut provided at the contact electrode support boundary and partly undercutting the contact electrode support area of the contact electrode support. This has the effect that the risk of short circuiting in the probe tip is further reduced.
The contact electrode support undercut may define a third undercutting depth being smaller than 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, or 50 nm.
The second trace support undercut and the contact electrode under having approximately the same undercutting depth. This has the advantage that the probe is easier to manufacture.
The contact electrode support area may be convex. This has the effect that the contact electrodes do not present any sharp corners or edges, and it is contemplated that the risk is reduced that small short circuiting particles will get stuck between closely positioned contact electrodes. Further, the risk of sharp corners or edges damaging a test sample and causing short circuiting particles to be released is reduced. Also, the convexity means that it is most likely that a test sample is contacted by the centre of the contact element, which increases the accuracy and precision of the contacting.
The above objects are according to a second aspect of the present invention obtained by a probe tip for establishing an electrical contact to test sample, the probe tip comprising: a tip base having a proximal end and a distal end and constituting a plate-like tip structure defining a top surface, a bottom surface, and a rim interconnecting the top surface and the bottom surface, the top surface connecting to the rim along a first side edge extending from the proximal end to the distal end, a second side edge on the opposite side of the tip structure relative to the first side edge and extending from the proximal end to the distal end, and a front edge interconnecting the first side edge and the second side edge, a first plurality of contact electrodes for contacting and establishing an electrical connection to the test sample, a second plurality of contact electrode supports provided on the second top surface and supported by the tip base, each contact electrode support being elongated and extending from the proximal end in a direction towards the distal end, and each contact electrode support having an outline defining a contact electrode support boundary enclosing a contact electrode support area, and each contact electrode of the first plurality of contact electrodes being individually supported by a contact electrode support of the second plurality of contact electrode supports and being constituted by a metallic electrode layer covering the contact electrode support area of the supporting contact electrode support, the first plurality and the second plurality being equal in numbers, the top surface comprising intermediate surfaces, each intermediate surface individually interconnecting a pair of neighbouring contact electrode supports of the second plurality of contact electrode supports, and the intermediate surfaces being provided on a first level, the contact electrode support areas being provided on a second level above the first level relative to the tip base.
The intermediate surfaces being provided on a first level and the contact electrode support areas being provided on a second level has the effect that the risk for short circuiting in the probe tip as such is reduced. Further, particles may get stuck on the probe tip when it is repeatedly used. The contact electrodes protrude from the tip base, which reduces the risk that particles on the test sample will get stuck on the fourth intermediate surfaces of the second top surface, which means that the risk of particles short circuiting the probe arms in repeated measurements is reduced.
The front edge may be straight. This has the advantage that the risk of contacting the test sample with the tip base is reduced, which could damage the test sample and cause particles to be released from the test sample that would land on the multi-point probe and cause it to short circuit.
The second plurality of electrode supports may extend to and terminates at the front edge. This further reduces the risk of damaging the test sample and generating short circuiting particles when contacting a test sample.
The second plurality of electrode supports extends to and terminates at a distance from the front edge. This has the effect that the distal ends of the contact electrodes can be defined independent of the front edge, which means that their positions can be more accurately determined, thus increasing the accuracy of the contacting.
The distance may be in one or more of the ranges 0.1 μm to 2 μm, 0.2 μm to 1.5 μm, 0.3 μm to 1 μm, 0.4 μm to 0.9 μm, 0.5 μm to 0.8 μm, 0.6 μm to 0.7 μm, 0.1 μm to 0.2 μm, 0.2 μm to 0.3 μm, 0.3 μm to 0.4 μm, 0.4 μm to 0.5 μm, 0.5 μm to 0.6 μm, 0.6 μm to 0.7 μm, 0.7 μm to 0.8 μm, 0.8 μm to 0.9 μm, 0.9 μm to 1 μm, 1 μm to 1.5 μm, and 1.5 μm to 2 μm.
Each contact electrode support of the second plurality of contact electrode supports may define a contact electrode support undercut provided at the contact electrode support boundary and partly undercutting the contact electrode support area of the contact electrode support. This has the effect that the risk of short circuiting in the probe tip is further reduced.
The contact electrode support undercut may define an undercutting depth being smaller than 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, or 50 nm.
The contact electrode support area may be convex. This has the effect that the contact electrodes do not present any sharp corners or edges, and it is contemplated that the risk is reduced that small short circuiting particles will get stuck between closely positioned contact electrodes. Further, the risk of sharp corners or edges damaging a test sample and causing short circuiting particles to be released is reduced. Also, the convexity means that it is most likely that a test sample is contacted by the centre of the contact element, which increases the accuracy and precision of the contacting.
The first level and the second level may be spaced apart by a first distance, and the first distance is smaller than 2 μm, 1.5 μm, 1 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, or 0.3 μm.
The above objects are according to a third aspect of the present invention obtained by a method for manufacturing a multipoint probe, the method comprising: providing a wafer comprising a bottom layer of a first material, an intermediate layer of a second material, and a top layer of a third material, and the bottom layer, the intermediate layer, and the top layer being arranged in a sandwiched structure, covering the top layer with a first mask corresponding in coverage to the contact pad support areas of the second plurality of contact pad supports and the trace support areas of the third plurality of trace supports, performing a first etching of the top layer for removing all the top layer that is not protected by the first mask, removing the first mask, and subsequently performing a second etching of the intermediate layer for removing a second amount of the intermediate layer that is not covered by the remaining top layer and for providing the narrow portions of the third plurality of trace supports and the second intermediate surfaces, or alternatively performing a second etching of the intermediate layer for removing a second amount of the intermediate layer that is not covered by the remaining top layer and for providing the narrow portions of the third plurality of trace supports and the second intermediate surfaces and subsequently removing the first mask, covering the intermediate layer with a second mask corresponding in coverage to the narrow portion of each of the third plurality of trace supports and the second intermediate surfaces, performing a third etching the intermediate layer for removing a third amount of the intermediate layer that is not protected by the second mask and for providing the second plurality of contact pad supports, the wide portions of the third plurality of trace supports and the first intermediate surfaces, removing the second mask, covering the remaining top layer and the remaining intermediate layer with a third mask corresponding in coverage to the top surface and the probe tip, performing a fourth etching for removing the remaining parts of the intermediate layer and the top layer that are not protected by the third mask, removing the third mask, covering the bottom layer on the opposite side as the intermediate layer with a fourth mask corresponding in coverage to the bottom surface, performing a fifth etching for removing the parts of the bottom layer that are not protected by the fourth mask for providing the circumferential first rim, the first bottom surface, and the probe tip freely extending from the circumferential first rim, and depositing a metallic film on the remaining top layer and the remaining intermediate for providing the first plurality of contact electrodes, the fourth plurality of contact pads, and the fifth plurality of traces.
The multipoint probe may be a multi point probe according to the first aspect of the present invention. The fourth etching may further be performed for providing the rim of the tip base and the sixth plurality of electrode supports terminating at the front edge. Alternatively, the fourth etching may further be performed for providing the rim of the tip base and the sixth plurality of electrode supports terminating at a third distance from the front edge.
The first material may be crystalline silicon, the second material may be silicon dioxide, and the third material may be amorphous silicon layer.
The method may further comprise prior to covering the remaining top layer and the remaining intermediate layer with a third mask: subjecting the top layer to an oxidation for transforming the third material to silicon dioxide.
The oxidation has the effect that the intermediate layer and the top layer are of similar materials albeit provided separately. This means that internal stresses between the different layers of the probe tip may be reduced, which reduces the risk of delamination of the intermediate and top layers, and also the risk for deformation of the probe tip as a whole.
The subjecting of the top layer to an oxidation may further provide the trace support area being convex at the narrow portions of each trace support of the third plurality of trace supports. The subjecting of the top layer to an oxidation may further be for providing the contact electrode support area being convex. The subjecting of the top layer to an oxidation may further be for providing the second trace support undercut of each trace support of the third plurality of trace supports. This has the effect that the risk for short circuiting is reduced when depositing the metallic film.
The subjecting of the top layer to an oxidation may further be for the providing of the contact electrode support undercuts of each contact electrode support of the sixth plurality of contact electrode supports. This has the effect that the risk for short circuiting is reduced when depositing the metallic film.
The oxidation may comprise a wet oxidation with water at a temperature between 900 C and 1150 C, or at a temperature of 950 C.
The bottom layer may have a thickness greater than 50 μm, 100 μm, 150 μm, 200, or 300 μm, and the intermediate layer may have a thickness in one or more of the ranges 1 μm to 2 μm, 1.1 μm to 1.9 μm, 1.2 μm to 1.8 μm, 1.3 μm to 1.7 μm, 1.4 μm to 1.6 μm, 1.1 μm to 1.2 μm, 1.2 μm to 1.3 μm, 1.3 μm to 1.4 μm, 1.4 μm to 1.5 μm, 1.5 μm to 1.6 μm, 1.6 μm to 1.7 μm, 1.7 μm to 1.8 μm, 1.8 μm to 1.9 μm, and/or 1.9 μm, to 2 μm, and the top layer may have a thickness in one or more of the ranges 20 nm to 150 nm, 30 nm to 140 nm, 40 nm to 130 nm, 50 nm to 120 nm, 60 nm to 110 nm, 70 nm to 100 nm, 80 nm to 90 nm, 20 nm to 30 nm, 30 nm to 40 nm, 40 nm to 50 nm, 50 nm to 60 nm, 60 nm to 70 nm, 70 nm to 80 nm, 80 nm to 90 nm, 90 nm to 100 nm, 100 nm to 110 nm, 110 nm to 120 nm, 120 nm to 130 nm.
The first etching may be a vertical dry etching adapted for selectively etching the first material. A vertical etching is here and throughout the specifications understood to provide an etching in a direction normal to the one or more layer of a wafer. This means that the vertical etching provides no, or an insignificant, undercutting of the etched structures. The first etching may comprise a first deep reactive ion etch. The first deep reactive ion etch may comprise C4F8 and SF6 gases.
The second etching may be a vertical dry etching and adapted for selectively etching the second material The second etching may comprise a second deep reactive ion etch. The second deep reactive ion etch may comprise C4F8 gas. The first etching and the second etching may define a first etching depth in the second material that is smaller than 2 μm, 1.5 μm, 1 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, or 0.3 μm. The first etching and the second etching may define the third distance.
The third etching may be an etching adapted for selectively etching the second material. The third etching may comprise a first wet etch. This has the effect that undercuttings can be provided in the non-masked portions. The first wet etch may comprise buffered hydrogen fluoride. The third etching in addition to the second etching may provide a second etching depth in the second material that is greater than 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, or 2 μm. The third etching may provide the first trace support undercut of each trace support of the third plurality of trace supports.
The fourth etching may be an etching adapted for selectively etching the second material. The fourth etching may comprise a third deep reactive ion etch. The fourth deep reactive ion etch may comprise C4F8 gas.
The fifth etching may be an etching adapted for selectively etching the third material. The fifth etching may comprise a second wet etch. The second wet etch comprises a potassium hydroxide solution.
The method according to the third aspect of the present invention may further comprise prior to performing the fifth etching: covering the whole of the remaining top layer, the remaining intermediate layer, and the bottom layer with a protective film, and removing one or more portions of the protective film on the bottom layer on the opposite side of the intermediate layer for providing the fourth mask. Said protective film may comprise a silicon nitride layer and the one or more portions of the protective film may be removed by photolithography involving vertical dry etching.
The method according to the third aspect of the present invention may further comprise prior to covering the intermediate layer with a second mask: performing an additional etching for providing the second trace support undercut of each trace support of the third plurality of trace supports. The additional etching may further be for providing the contact electrode support undercuts of each contact electrode support of the sixth plurality of contact electrode supports. The additional etching may be an etching adapted for selectively etching the second material. The additional etching may comprise an additional wet etch. This has the effect that undercuttings can be provided in the non-masked portions. The additional wet etch may comprise buffered hydrogen fluoride.
The above objects are according to a fourth aspect of the present invention obtained by a method for manufacturing a probe tip, the method comprising: providing a wafer comprising a bottom layer of a first material, an intermediate layer of a second material, and a top layer of a third material, and the bottom layer, the intermediate layer, and the top layer being arranged in a sandwiched structure, covering the top layer with a first mask corresponding in coverage to the second plurality of contact electrode supports, performing a first etching of the top layer for removing all the top layer that is not protected by the first mask, removing the first mask and subsequently performing a second etching of the intermediate layer for removing a second amount of the intermediate layer that is not covered by the remaining top layer and for providing the second plurality of contact electrode supports and the intermediate surfaces, or alternatively performing a second etching of the intermediate layer for removing a second amount of the intermediate layer that is not covered by the remaining top layer and for providing the second plurality of contact electrode supports and the intermediate surfaces and subsequently removing the first mask, covering the remaining top layer and the remaining intermediate layer with a second mask corresponding in coverage to the top surface and the probe tip, performing a third etching for removing the remaining parts of the intermediate layer and the top layer that are not protected by the second mask and for providing the rim of the tip base, removing the second mask, performing a fourth etching for removing the bottom layer for providing the bottom surface, and depositing a metallic film on the remaining top layer and the remaining intermediate for providing the first plurality of contact electrodes.
The probe tip may be a probe tip according to the second aspect of the present invention. The third etching may further be performed for providing the front edge being straight. The third etching may further be performed for providing the sixth plurality of electrode supports terminating at the front edge. Alternatively, the third etching may further be performed for providing the sixth plurality of electrode supports terminating at a third distance from the front edge.
The first material may be crystalline silicon, the second material may be silicon dioxide, and the third material may be amorphous silicon layer.
The method according to the fourth aspect of the present invention may further comprise prior to covering the remaining top layer and the remaining intermediate layer with a second mask: subjecting the top layer to an oxidation for transforming the third material to silicon dioxide.
The oxidation has the effect that the intermediate layer and the top layer are of similar materials, even though they have been provided separately. This means that internal stresses may be reduced, which reduces the risk of delamination of the intermediate and top layer when flexing the probe tip in a contacting, and also the risk for deformation of the probe tip as a whole. This may also mean that if the third etching is selective to the second material of the intermediate layer, it is also selective to the oxidized material of the top layer. This has the advantage that the top layer and the intermediate layer define a common edge provided in a single etching step. This means that structures provided from the top layer, such as a contact electrode support, may be positioned exactly at the edge of the underlying structure from the intermediate layer, such as a tip base.
The subjecting of the top layer to an oxidation may further be for providing the contact electrode support area being convex. The subjecting of the top layer to an oxidation may further be for the contact electrode support undercuts of each contact electrode support of the sixth plurality of contact electrode supports. This has the effect that the risk for short circuiting is reduced when depositing the metallic film.
The oxidation may comprise a wet oxidation with water at a temperature between 900 C and 1150 C, or at a temperature of 950 C.
The bottom layer may have a thickness greater than 50 μm, 100 μm, 150 μm, 200, or 300 μm and the intermediate layer may have a thickness in one or more of the ranges 1 μm to 2 μm, 1.1 μm to 1.9 μm, 1.2 μm to 1.8 μm, 1.3 μm to 1.7 μm, 1.4 μm to 1.6 μm, 1.1 μm to 1.2 μm, 1.2 μm to 1.3 μm, 1.3 μm to 1.4 μm, 1.4 μm to 1.5 μm, 1.5 μm to 1.6 μm, 1.6 μm to 1.7 μm, 1.7 μm to 1.8 μm, 1.8 μm to 1.9 μm, and/or 1.9 μm to 2 μm, and the top layer may have a thickness in one or more of the ranges 20 nm to 150 nm, 30 nm to 140 nm, 40 nm to 130 nm, 50 nm to 120 nm, 60 nm to 110 nm, 70 nm to 100 nm, 80 nm to 90 nm, 20 nm to 30 nm, 30 nm to 40 nm, 40 nm to 50 nm, 50 nm to 60 nm, 60 nm to 70 nm, 70 nm to 80 nm, 80 nm to 90 nm, 90 nm to 100 nm, 100 nm to 110 nm, 110 nm to 120 nm, 120 nm to 130 nm.
The first etching may be a vertical dry etching adapted for selectively etching the first material. The first etching may comprise a first deep reactive ion etch. The first deep reactive ion etch may comprise C4F8 and SF6 gases.
The second etching may be a vertical dry etching and adapted for selectively etching the second material. The second etching may comprise a second deep reactive ion etch. The second deep reactive ion etch may comprise C4F8 gas.
The first etching and the second etching may define a first etching depth in the second material that is smaller than 2 μm, 1.5 μm, 1 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, or 0.3 μm.
The third etching may be an etching adapted for selectively etching the second material. The third etching may comprise a third deep reactive ion etch. The fourth deep reactive ion etch may comprise C4F8 gas.
The fourth etching may be an etching adapted for selectively etching the third material. The fourth etching may comprise a second wet etch. The second wet etch may comprise a potassium hydroxide solution.
The method according to the fourth aspect of the present invention may further comprise prior to performing the fourth etching: covering the whole of the remaining top layer and the remaining intermediate layer with a protective film. The protective film may comprise a silicon nitride layer.
The method according to the fourth aspect of the present invention may further comprise prior to covering the intermediate layer with a second mask: performing an additional etching for providing the contact electrode support undercuts of each contact electrode support of the sixth plurality of contact electrode supports. The additional etching may be an etching adapted for selectively etching the second material. The additional etching may comprise an additional wet etch. This has the effect that undercuttings can be provided in the non-masked portions. The additional wet etch may comprise buffered hydrogen fluoride.
In all of the above aspects of the present invention, the front edge and the tip base may be divided into a first and a second front edge portion and a first and a second tip base portions, respectively, by a first slit extending from the distal end in a direction towards the proximal end and provided between a pair of neighbouring contact electrodes of the first plurality of contact electrodes. The first slit may extend to approximately halfway between the proximal and the distal end. Alternatively, the first slit may extend to the proximal end.
The front edge may be is cut into a seventh plurality of portions by an eighth plurality of second slits, and each second slit extends in a direction from the distal end to the proximal end and is provided between a pair of neighbouring contact electrodes of the first plurality of contact electrodes 32. Each second slit may terminate at a point between half the front edge and halfway between the distal end and the proximal end. The first and second slits have the effect that internal stresses in the larger tip base 68 are avoided when contacting, in particular if a front corner between the front edge an one of the side edges first engages a test sample.
In all of the above aspects, the metallic film may comprise an adhesion layer of titanium or chromium provided on the wafer and a conductive layer of gold or nickel. The adhesion layer may be thinner than the conductive layer. The adhesion layer may be about 10 nm thick and the conductive layer may be about 100 nm thick.
In the first and second aspects of the present invention, an intermediate metallic layer may be provided on and covering the first, second, third and/or fourth intermediate surfaces. In the third and fourth aspects of the present invention, the depositing of the metal film may also provide an intermediate metallic layer on and covering the first, second, third and/or fourth intermediate surfaces.